Help with Countdown clock needed

Hi all,


I've adapted an actionscript I found on the net  and I wonder could someone tell me  how to make two small changes to it ?

When the time reaches 0 I want it to play a sound and the display to change to "Time Over". Also, I want the first frame to have a start button that when pressed begins the countdown.

The working file is at http://www.whatyouseeyoucannotbe.com/minute_countdowner.fla

Thanks,